The invention relates to a current supply apparatus for a load object, and, more particularly, to such an apparatus including means for periodically changing the polarity of the current that is supplied to the load object.
It is known to the art to supply current of periodically changing polarity to the windings of a synchronous machine to operate the machine. For example, in the U.S. Pat. No. 3,995,203, at FIG. 7 there is shown a reluctance machine having a power winding that is supplied with driving current from a DC current source. The winding has a center tap and the end of the windings are connected to the DC current source through thyristors.
The thyristors are operated to periodically conduct and to thereby change the direction of flow of the driving current through one-half of the winding. Since only one half of the winding is used to carry current at one time, the winding is not utilized in an efficient manner.
FIG. 8 of the above prior art patent shows a bridge circuit having four thyristors for supplying alternating current to the winding of a synchronous machine. In operation, pairs of diagonally opposite thyristors are operated to alternately conduct to periodically change the direction of flow of current in the associated power winding. However, such a power supply apparatus is necessarily complicated and expensive since four thyristors having associated cooling bodies, fuses, control devices and overvoltage protection devices are required to operate to supply the alternating current to the power winding.
Accordingly, it is an object of the invention to provide a relatively simple and efficient apparatus for supplying current of changing polarity to the power windings of a synchronous machine.
Another object of the invention is to provide such an apparatus wherein a minimum number of switching elements are used to change the direction of flow of the supply current and to pass the supply current through an entire power winding to efficiently utilize the winding.
A further object of the invention is to provide an improved current supply apparatus wherein a single thyristor is used to provide current for each phase of a multi-phase load object.
Another object of the invention is to provide an improved current supply apparatus wherein current smoothing elements in a supplying DC circuit are either reduced in size or eliminated.
These and other objects of the invention will become apparent from a review of the detailed specification which follows and a consideration of the accompanying drawings.